1. Field of the Invention
This invention relates to a novel synthetic resin (plastic) needle having a high stiffness and toughness. In particular, it relates to a medical plastic needle, such as an intra-venous needle, an intra-venous catheter, a blood sampling needle or a needle of administration set.
2. Description of Background Art
A metal such as stainless steel is generally employed as a material for an intra-venous needle. An intra-venous needle made of a metal is certainly advantageous in that the wall thickness of the needle can be made very thin so that a large flow rate can be secured even if the diameter of the needle is rather small and the needle edge can be sharply abraded so that smooth piercing by the needle can be achieved. However, since an intra-venous needle made of a metal can not be discarded as combustible waste after use, it is disposed of after use in its original form. Accordingly, the development of a combustible intra-venous needle would be highly desirable. In order to meet this, we have studied the use of synthetic resins for an intra-venous or other needle.
When an intra-venous needle is solely composed of a synthetic resin however, it is difficult to obtain sufficient stiffness and strength to avoid deformation or breakage of the edge of the synthetic resin needle, which detract from the capacity of the needle to penetrate easily. On the other hand, when a filler is added to the synthetic resin needle with a view to improving the stiffness of the needle, the toughness of the needle may instead be lowered though the stiffness of the needle may be improved, thereby increasing on the contrary the possibility of the needle being broken during penetration.
Accordingly, the problem faced is to develop a synthetic resin needle having a sufficient stiffness and at the same time a sufficient toughness to withstand actual usage as, e.g., an intra-venous needle and at the same time being capable of being disposed as combustible waste after use.